The face-down soldering of integrated circuit (IC) devices to chip carriers, known as “flip-chip packaging” has been used in the semiconductor manufacturing process for forty years. Injection Molding Soldering (IMS) is a technique developed by IBM to address the cost vs. quality issues associated with current wafer bumping technologies. IMS as applied to wafer bumping has been dubbed C4NP (Controlled Collapse Chip Connection New Process) and is the newest semiconductor packaging technology developed by IBM for putting C4 solder bumps onto chips at the wafer level using a lead-free solder.
C4NP involves filling specially designed pits in a solder mold (mold plate) using a head which provides molten solder. The solder is typically constrained to the head and operating area by an o-ring that is compressed between the fill head and the mold plate. This interface between the fill head and the mold plate must be moved onto the mold plate from a parking location of some sort, as the head must remain at operating temperature (with the solder molten). This is done by moving the head across a seam between the mold plate and the parking area, stressing and often damaging the o-ring. This limits the machine throughput, as o-ring replacement is a lengthy process. In addition, o-rings are stressed and damaged by reversals in motion and direction, so any solution would be best if it was implemented in a unidirectional way. It would also be beneficial if in any solution for the interface cleaning process could be accomplished without machine downtime.